Mobile nodes, which have become widely used in society today, may take a variety of forms. For example, the mobile node may be a cellular phone or personal communication service (PCS) device.
A mobile node may be coupled directly or indirectly to a wireless network. In turn, the wireless network may be directly or indirectly coupled to another device. The mobile node may wish to communicate with this other device.
The mobile node may be also coupled to a user device. The user device may be any device that is capable of transmitting and/or receiving any type of information. For instance, the user device may be a personal digital assistant (PDA) or a personal computer. Other types of user devices are possible.
Mobile nodes may travel within a “home” network and travel to other (“foreign”) networks. Wherever the mobile node is located, other users and entities may need to send information to the mobile node and the mobile node may desire to send information to these other users and entities.
In order to determine the location of the mobile node (and transfer the information), the mobile node may be given a permanent address (“home address”) on the home network. When away from its home network, the current address (“care-of address”) associated with the mobile node may reflect the mobile node's current point of attachment within the foreign network. The mobile node may use its home address as the source address of all information, for example, IP datagrams that the mobile node sends or receives from other users or entities.
To facilitate the transfer of information between the mobile node and other users and entities, the home network may include a home agent. The home agent may perform several functions. For example, the home agent may maintain information concerning the mobile node, for instance, the current location of the home device. In another example, when another user or entity desires to communicate with the mobile node, the home agent may act as a router and “tunnel” information to the mobile node (when the mobile node is attached to a foreign network).
The foreign network may include a foreign agent, which may also perform several functions. For example, when a mobile node moves to the foreign network, the mobile node may contact the foreign agent. In one illustrative example, the foreign agent may be a router on the foreign network and provide routing services to the mobile node while the mobile node is registered on the foreign network. The foreign agent may also “detunnel” and deliver information to the mobile node that was tunneled by the mobile node's home agent.
Home agents and foreign agents may advertise their availability on each network for which they provide service. A newly arrived mobile node may send a solicitation on the foreign network to learn if any prospective foreign agents are present. When the mobile node is away from its home network, it may register its care-of address with its home agent. Depending on its method of attachment, the mobile node may register either directly with its home agent, or through a foreign agent, which forwards the registration to the home agent.
Upon the traversal of a serving area by a mobile node, the mobile node must register with a new foreign agent. Transfer of session from one foreign agent to another may be performed using a proxy server to re-establish the mobile node user's profile information, and the home agent to re-establish the connection profile for the session.